Rules and Regulations. Final special conditions; request for comments

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BILLING CODE 3410-34-P DEPARTMENT OF TRANSPORTATION Federal Aviation Administration 14 CFR Part 25 [Docket No. NM240, Special Conditions No. 25-227-SC] Special Conditions: Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F Airplanes; High Intensity Radiated Fields

(HIRF)AGENCY: Federal Aviation Administration (FAA), DOT. ACTION: Final special conditions; request for comments. SUMMARY: These special conditions are issued for Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air, Inc. These airplanes, as modified, will have novel and unusual design features when compared to the state of technology envisioned in the airworthiness standards for transport category airplanes. The modification incorporates the installation of the Innovative Solutions & Support (IS&S) Air Data Display Units

(ADDU)and Air Data Sensor. The applicable airworthiness regulations do not contain adequate or appropriate safety standards for the protection of these systems from the effects of high-intensity-radiated fields (HIRF). These special conditions contain the additional safety standards that the Administrator considers necessary to establish a level of safety equivalent to that established by the existing airworthiness standards. DATES: The effective date of these special conditions is February 21, 2003. Comments must be received on or before April 2, 2003. ADDRESSES: Comments on these special conditions may be mailed in duplicate to: Federal Aviation Administration, Transport Airplane Directorate, Attn: Rules Docket (ANM-113), Docket No. NM240, 1601 Lind Avenue SW., Renton, Washington 98055-4056; or delivered in duplicate to the Transport Airplane Directorate at the above address. Comments must be marked: Docket No. NM240. Comments may be inspected in the Rules Docket weekdays, except Federal holidays, between 7:30 a.m. and 4 p.m. FOR FURTHER INFORMATION CONTACT: Greg Dunn, FAA, Airplane and Flight Crew Interface Branch, ANM-111, Transport Airplane Directorate, Aircraft Certification Service, 1601 Lind Avenue SW., Renton, Washington 98055-4056; telephone

(425)227-2799; facsimile

(425)227-1149. SUPPLEMENTARY INFORMATION: FAA's Determination as to Need for Public Process The FAA has determined that notice and opportunity for prior public comment are unnecessary in accordance with 14 CFR 11.38, because the FAA has provided previous opportunities to comment on substantially identical special conditions and has fully considered and addressed all the substantive comments received. Based on a review of the comment history and the comment resolution, the FAA is satisfied that new comments are unlikely. The FAA, therefore, finds that good cause exists for making these special conditions effective upon issuance. However, the FAA invites interested persons to participate in this rulemaking by submitting comments, data, or views. The most helpful comments reference a specific portion of the special conditions, explain the reason for any recommended change, and include supporting data. We ask that you send us two copies of written comments. We will file in the docket all comments we receive, as well as a report summarizing each substantive public contact with FAA personnel concerning these special conditions. The docket is available for public inspection before and after the comment closing date. If you wish to review the docket in person, go to the address in the ADDRESSES section of this preamble between 7:30 a.m. and 4 p.m., Monday through Friday, except Federal holidays. We will consider all comments we receive on or before the closing date for comments. We will consider comments filed late if it is possible to do so without incurring expense or delay. We may change these special conditions in light of the comments we receive. If you want the FAA to acknowledge receipt of your comments on this proposal, include with your comments a pre-addressed, stamped postcard on which the docket number appears. We will stamp the date on the postcard and mail it back to you. Background On August 17, 2002, Royal Air, Inc., 2141 Airport Road, Waterford, Michigan 48327, applied for a supplemental type certificate

(STC)to modify Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes approved under Type Certificate No. A10CE. The Learjet Model 24/25 series airplanes are small transport category airplanes powered by two turbojet engines, with maximum takeoff weights of up to 15,000 pounds. These airplanes operate with a 2-pilot crew and can seat 6 to 8 passengers. The modification incorporates the installation of the Innovative Solutions & Support (IS&S) Air Data Display Units

(ADDU)and Air Data Sensor. The ADDU digital air data computing altimeter provides flight critical functions. These advanced systems have the potential to be vulnerable to high-intensity radiated fields

(HIRF)external to the airplane. Type Certification Basis Under the provisions of 14 CFR 21.101, Amendment 21-69, effective September 16, 1991, Royal Air must show that the Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes, as changed, continue to meet the applicable provisions of the regulations incorporated by reference in Type Certificate No. A10CE, or the applicable regulations in effect on the date of application for the change. Subsequent changes have been made to § 21.101 as part of Amendment 21-77, but those changes do not become effective until June 10, 2003. The regulations incorporated by reference in the type certificate are commonly referred to as the “original type certification basis.” The original type certification basis for the modified Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes includes 14 CFR part 25, dated February 1, 1965, through Amendments 25-2 and 25-4; and 14 CFR part 25, dated February 1, 1965, through Amendment 25-18, except for special conditions and exceptions noted in Type Certificate Data Sheet

(TCDS)A10CE. If the Administrator finds that the applicable airworthiness regulations ( *i.e.* , 14 CFR part 25, as amended) do not contain adequate or appropriate safety standards for the Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes because of novel or unusual design features, special conditions are prescribed under the provisions of § 21.16. In addition to the applicable airworthiness regulations and special conditions, the Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes must comply with the fuel vent and exhaust emission requirements of 14 CFR part 34 and the noise certification requirement of part 36, including Amendment 36-1. Special conditions, as defined in § 11.19, are issued in accordance with § 11.38, and become part of the type certification basis in accordance with § 21.101(b)(2). Special conditions are initially applicable to the model for which they are issued. Should Royal Air apply at a later date for design change approval to modify any other model already included on the same type certificate to incorporate the same or similar novel or unusual design feature, these special conditions would also apply to the other model under the provisions of § 21.101(a)(1). Novel or Unusual Design Features As noted earlier, the Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes will incorporate new Air Data Display Units

(ADDU)and Air Data Sensor that will perform critical functions. These systems have the potential to be vulnerable to high-intensity radiated fields

(HIRF)external to the airplane. The current airworthiness standards (14 CFR part 25) do not contain adequate or appropriate safety standards for the protection of this equipment from the adverse effects of HIRF. Accordingly, this system is considered to be a novel or unusual design feature. Discussion There is no specific regulation that addresses protection requirements for electrical and electronic systems from HIRF. Increased power levels from ground-based radio transmitters and the growing use of sensitive avionics/electronics and electrical systems to command and control airplanes have made it necessary to provide adequate protection. To ensure that a level of safety is achieved equivalent to that intended by the regulations incorporated by reference, special conditions are needed for the Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air, Inc. These special conditions require that new avionics/electronics and electrical systems that perform critical functions be designed and installed to preclude component damage and interruption of function due to both the direct and indirect effects of HIRF. High-Intensity Radiated Fields

(HIRF)With the trend toward increased power levels from ground-based transmitters, plus the advent of space and satellite communications, coupled with electronic command and control of the airplane, the immunity of critical digital avionics/electronics and electrical systems to HIRF must be established. It is not possible to precisely define the HIRF to which the airplane will be exposed in service. There is also uncertainty concerning the effectiveness of airframe shielding for HIRF. Furthermore, coupling of electromagnetic energy to cockpit-installed equipment through the cockpit window apertures is undefined. Based on surveys and analysis of existing HIRF emitters, an adequate level of protection exists when compliance with the HIRF protection special condition is shown with either paragraph 1 or 2 below: 1. A minimum threat of 100 volts rms (root-mean-square) per meter electric field strength from 10 KHz to 18 GHz. a. The threat must be applied to the system elements and their associated wiring harnesses without the benefit of airframe shielding. b. Demonstration of this level of protection is established through system tests and analysis. 2. A threat external to the airframe of the field strengths indicated in the following table for the frequency ranges indicated. Both peak and average field strength components from the table are to be demonstrated. Frequency Field strength (volts per meter) Peak Average 10 kHz-100 kHz 50 50 100 kHz-500kHz 50 50 500 kHz-2 MHz 50 50 2 MHz-30 MHz 100 100 30 MHz-70 MHz 50 50 70 MHz-100 MHz 50 50 100 MHz-200 MHz 100 100 200 MHz-400 MHz 100 100 400 MHz-700 MHz 700 50 700 MHz-1 GHz 700 100 1 GHz-2 GHz 2000 200 2 GHz-4 GHz 3000 200 4 GHz-6 GHz 3000 200 6 GHz-8 GHz 1000 200 8 GHz-12 GHz 3000 300 12 GHz-18 GHz 2000 200 18 GHz-40 GHz 600 200 The field strengths are expressed in terms of peak of the root-mean-square

(rms)over the complete modulation period. The threat levels identified above are the result of an FAA review of existing studies on the subject of HIRF, in light of the ongoing work of the Electromagnetic Effects Harmonization Working Group of the Aviation Rulemaking Advisory Committee. Applicability As discussed above, these special conditions are applicable to Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air, Inc. Should Royal Air apply at a later date for a supplemental type certificate to modify any other model included on the same type certificate to incorporate the same or similar novel or unusual design feature, these special conditions would apply to that model as well under the provisions of § 21.101(a)(1). Conclusion This action affects only certain design features on Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air. It is not a rule of general applicability and affects only the applicant who applied to the FAA for approval of these features on the airplane. The substance of the special conditions for these airplanes has been subjected to the notice and comment procedure in several prior instances and has been derived without substantive change from those previously issued. Because a delay would significantly affect the certification of the airplane, which is imminent, the FAA has determined that prior public notice and comment are unnecessary and impracticable, and good cause exists for adopting these special conditions upon issuance. The FAA is requesting comments to allow interested persons to submit views that may not have been submitted in response to the prior opportunities for comment described above. List of Subjects in 14 CFR Part 25 Aircraft, Aviation safety, Reporting and record keeping requirements. The authority citation for these special conditions is as follows: Authority: 49 U.S.C. 106(g), 40113, 44701, 44702, 44704 The Special Conditions Accordingly, pursuant to the authority delegated to me by the Administrator, the following special conditions are issued as part of the type certification basis for Learjet Model 24, 24A, 24B, 24B-A, 24C, 24D, 24D-A, 24E, 24F, 24F-A, 25, 25A, 25B, 25C, 25D and 25F airplanes modified by Royal Air, Inc. 1. Protection from Unwanted Effects of High-Intensity Radiated Fields (HIRF). Each electrical and electronic system that performs critical functions must be designed and installed to ensure that the operation and operational capability of these systems to perform critical functions are not adversely affected when the airplane is exposed to high intensity radiated fields external to the airplane. 2. For the purpose of these special conditions, the following definition applies: Critical Functions: Functions whose failure would contribute to or cause a failure condition that would prevent the continued safe flight and landing of the airplane. Issued in Renton, Washington, on February 21, 2003. Ali Bahrami, Acting Manager, Transport Airplane Directorate, Aircraft Certification Service. [FR Doc. 03-4796 Filed 2-28-03; 8:45 am]

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